THE USE OF LASERS AS A SURGICAL MODALITY HAS BEEN ESTABLISHED IN RECENT YEARS. LASERS OF VARIOUS WAVELENGTHS ARE SUITED FOR DIFFERENT SPECIFIC SURGICAL FUNCTIONS. CO2 (10.6 ) RADIATION HAS SMALL PENETRATION DEPTHS IN TISSUES. THIS LEADS TO HIGH SURFACE TEMPERATURES WHICH ARE DESIRABLE FOR TISSUE INCISION THROUGH EVAPORATION. ND:YAG LASERS (1.06 ) PROVIDE VOLUMETRIC TISSUE HEATING WHICH IS EFFECTIVE IN VASCULAR COAGULATION. IN THE TREATMENT OF TUMORS AND CANCEROUS TISSUES, CONCURRENT HEMOSTASIS AND INCISION ARE NECESSARY REQUIREMENTS FOR WIDESPREAD CLINICAL APPLICATIONS OF LASERS AS SURGICAL TOOLS. THE SPECIFIC AIM OF THIS PROPOSED EFFORT IS DIRECTED TOWARDS THE DEVELOPMENT OF A NEW SURGICAL LASER SYSTEM CAPABLE OF PROVIDING THESE SIMULTANEOUS FUNCTIONS. THE SYSTEM HAS THE ADVANTAGES OF A SINGLE POWER SUPPLY AND ONE LASER HEAD. IT CAN PROVIDE THE ADDED FUNCTION OF CUTTING, WHICH ND-YAG ALONE CANNOT SUITABLY PERFORM. IT SHOULD ACCOMPLISH HEMOSTASIS OF VASCULAR REGIONS WHERE CO2 IS NOT ADEQUATE. IN ADDITION, AN IMPORTANT FEATURE IS ITS COMPATIBILITY WITH CONVENTIONAL QUARTZ FIBER OPTICS DELIVERY SYSTEM. SUCH A LASER WILL HAVE WIDESPREAD CLINICAL APPLICATIONS AND COMMERCIAL POTENTIAL. THIS RESEARCH EFFORT NATURALLY FALLS WITHIN THE REALM OF PROGRAM ACTIVITIES SPONSORED BY THE DIVISION OF CANCER TREATMENT, NATIONAL CANCER INSTITUTE. THE OBJECTIVES OF THIS PHASE I PROGRAM ARE TWO FOLD. (1) A COMPLETE DESIGN AND ANALYSIS OF THE LASER SYSTEM CAPABLE OF DELIVERING THE NECESSARY POWERS AT 1.06 AND 1.9 WILL BE PERFORMED. (2) EXPERIMENTS WILL BE CONDUCTED TO DETERMINE TISSUE ABSORPTION AND INTERACTION CHARACTERISTICS AT 1.9 , THUS VERIFYING THE POWER LEVELS NECESSARY FOR INCISION. RESULTS FROM PHASE I WILL PROVIDE THE BASIS FOR A PHASE II PROGRAM TO FABRICATE THIS LASER AND CONDUCT IN VIVO ANIMAL EXPERIMENTS.